Re: [PATCH] wc: line-buffer the printed counts

[Pádraig Brady]

On 22/12/09 09:38, Jim Meyering wrote:
> Pádraig Brady wrote:
> > wc is a essentially a digesting function like sha etc.
> > in that it produces a 1 line summary per file.
> > The attached patch ensures that those lines are output
> > atomically for concurrent wc processes.
> >
> > Note in general one can use `stdbuf -oL cmd` to line-buffer
> > a process which outputs to stdout, but I think this
> > should be done internally in this case.
> ...
> > +  wc now prints counts atomically so that concurrent
> > +  processes will not intersperse their output.
> > +  [the bug dates back to the initial implementation]
>
> Nice.  Thanks!
> You might want to cast this as an improvement, rather than a bug fix.

Well the related md5sum change was cast as a fix,
and it is just fixing an issue with running in parallel,
and we are just going for a bug fix release now.
So I'm inclined to leave it as a fix.

> This made me think of doing the same for du, but I'm hesitant.
> Many tools parse a single (voluminous) stream of du output,
> and forcing that to be line-buffered sounds like it'd impose
> too much of a penalty.

I noticed that du has always called fflush() after each entry,
which handles the issue also. I said I wouldn't change to
calling setvbuf as du is also outputting NUL terminated entries.

cheers,
Pádraig.